Automatic grinding machine

ABSTRACT

A method and an apparatus for performing the method characterized by forming a plurality of locating surfaces on a workpiece during a grinding cycle, positioning a new workpiece and repeating the grinding cycle to form identical locating surfaces thereon. The apparatus utilizes a control means which moves grinding wheels across their respective dress blocks in a predetermined sequence during each cycle prior to grinding the workpiece. The control means then actuates feed means on each of the grinding wheels to advance the respective grinding wheels in a predetermined axial distance for a subsequent dressing during the next grinding cycle and the control means positions a new workpiece in position relative to the dress blocks for a new grinding cycle. The apparatus utilizes a workholder which holds three workpieces in spaced relationship and the control means after performing the grinding cycle on each of the workpieces stops the operation of the machine.

United States Patent 1 4, 51

Mueller T Dec. 5, 1972 [54] AUTOMATIC GRINDING MACHINE [57] V ABSTRACT Inventor: Charles L- Mueller, Harrisburg, Pa. A method and an apparatus for performing the [73] Assisnee: TRw inc Cleveland, Ohio method characterized by forming a plurality of locatmg surfaces on a workpiece during a grinding cycle, Flledi 26, 1970 positioning a new workpiece and repeating the grind- [21] AWL 67,069 ing cycle to form identical locating surfaces thereon. The apparatus utilizes a control means which moves grinding wheels across their respective dress blocks in [52] US. Cl. ..51/5, 51/ 134,55ll//l9285.55, a predetermined sequence during each Cycle prior to d' th k Th t 1 th [51] int. Cl. ..B24b 7/00, 824b, 9/00, B24b 5/00 555 f gg ff ji [58] Field of Search ..51/5, 55, 56, 134, 165.87,

98 5 125 5 98 R 98 BS 98 HK 98 SP vance the respective grinding wheels in a predetermined axial distance for a subsequent dressing during the next grinding cycle and the control means p0si- [56] References Cited tions a new workpiece in position relative to the dress UNITED STATES PATENTS blocks for a new grinding cycle. The apparatus utilizes a workholder which holds three workpieces in spaced 1 1g glglrliely et al. ..51/98 115K117; zlellationsihip andl the congroi rtrieans lafter performigg t t t t 1,881,244 10/1932 Raule ..51/3 UX o e wot plecess Ops e 2,976,649 3/1961 Standal ..51/55 3,430,388 3/1969 Gabrielli ..51/3

Primary Examiner .lames L. Jones, Jr. Attorney-Hill, Sherman, Meroni, Gross & Simpson 10 Claims, 7 Drawing Figures r /0 i a; la/ 1 I J ,j 00 i7 .57 5 I a 4 M 56 4/ M i /7 127 z i as i II 2 i i 52 ff 3 l #4; i I54 .i 3/ H I 20 /9 49/ if Z9 O I I 27 2 Z 27 X4! z 3 J 3 /J;

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1 AUTOMATIC GRINDING MACHINE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a method and apparatus for sequentially forming a plurality of locating surfaces on a workpiece and particularly to a method and apparatus for repeating a predetermined grinding cycle on a plurality of workpieces in an automatic operation.

2. Prior Art In forming or machining workpieces or blanks such as raw casting or forgings for turbine blades, it is essential to provide locating faces or surfaces relative to the center of gravity of each of the workpiece for locating the workpiece in a subsequent finish machining operation for completing the turbine blade. In forming the locating surfaces, it is essential that these surfaces are properly oriented with respect to the center of gravity of each blade blank and that a minimum variation in the location of these surfaces occurs. Existing machining techniques for providing locating surfaces for positioning the workpiece in subsequent machining operations have been performed on individual units and have resulted in expensive machining operations which provides variations in the orientation or position of the locating surfaces on the workpieces.

SUMMARY OF THE INVENTION The present invention is directed to a method and an apparatus for perfonning the methodwhich forms a plurality of locating surfaces on a workpiece in a predetermined orientation to the workpiece in a predetermined cycle of sequential material removing steps. In the preferred embodiment material removing is by grinding utilizing a plurality of grinding means operating in a predetermined grinding sequence which is automatically repeated after positioning a new workpiece with respect to the grinding means.

Accordingly, it is an object of the present invention to provide a method and apparatus for removing material to form locating surfaces of the desired orientation on a workpiece.

Another object of the present invention is to provide a method and apparatus for forming locating surfaces on a workpiece during a material removing cycle and repeating this cycle to form similar surfaces on a second workpiece positioned with respect to the material removing means.

A still further object of the present invention is to provide a method and an apparatus which form a plurality of locating surfaces on a workpiece in a predetermined sequence of steps positioning a second workpiece, and then repeats thesequence of steps to form locating surface on the second workpiece,'and automatically stops after forming the locating surface on the last workpiece loaded in the apparatus.

Other objects, features and advantages of this invention will be readily apparent from the following description of the preferred embodiments thereof taken in conjunction with the accompanying drawings although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS in the present invention; and

FIG. 7 is a side elevational view of the apparatus of FIG. 1, with portions removed for purpose of illustration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the principles of the present invention are of utility for removing material to form locating surfaces on a workpiece, the principles are particularly useful when incorporated in a grinding apparatus generally indicated at 10 in'FIG. l for accomplishing the method.

The grinding apparatus has a frame means 11 having a table surface 12 supported by legs 13 having cross members 14. The frame means also has an upstanding portion 15 as illustrated in FIG. 2 which is adjacent the rear edge of the table portion 12.

Pivotally supported on the upstanding frame portion 15 are a pair of material removing means which are illustrated as grinding means 16 and 17. Pivotally supported on the table 12 is a third material removing means illustrated as a grinding means 18. The apparatus 10 also includes positioning means generally indicated at 19, dressing means which are diamond dressing blocks 20, 21 and 22 each associated with the respective grinding means l6, l7 and 18 and control means including a cabinet 23 and a switch box 24. To pivot the grinding means 16, 17 and 18 and to move the positioning means 19 a hydraulic systemv is provided and a hydraulic motor-pump assembly 25 of. the hydraulic system is disposed on the lower portion of the frame 1 l.

Each of the grinding means 16 and 17 is substantially similar in its construction and includes a grinding wheel 27, 27a mounted on a shaft 28, 28a which is telescopically disposed in a tubular shaft 29, 29a and extends to a spindle drive means contained in a housing 30, 30a respectively. The tubular shafts 29, 29a are supported for axial movement in a bearing contained in the housing 31 and 31a, respectively, which is secured to arms 32 and 32a, of actuating means 33 and 33a, respectively. Each of the grinding means 16, 17 includes a feed means 34 and 34a, respectively, which axially shifts the respective grinding means 16 or 17 relative to its bearing housing 31 or 31a. Feed means 34 and 34a couples their respective grinding means 16 and 17 to the arm 32 or 32a and can include appropriate means for axially shifting the grinding means 16 and 17 in increments of approximately 0.001 inches when desired. An example of a means for axially shifting the grinding means in the desired increment is an adjustable compensating unit utilizing a hydraulic ram and cylinder for shifting the grinding unit along its axis.

As mentioned above, the grinding means 16 and 17 are mounted on the vertical upright frame structure 15 in a pivotable manner by actuating means 33 and 33a respectively. As bestillustrated in F IG. 2,-the actuating means 33 includes a cylinder 36 pivotally attached to a second arm 37 and has a piston rod 38 which is pivotally connected to the upstanding frame 15. The arms 32 and 37 are rigidly interconnected and pivotally connected to a portion of the frame 15 by a pivot means 39 so that as the cylinder 36'moves with respect to its piston, the arms 32 and 37 pivotabout their connection 39 to the frame portion 15. With the movement of the arms 32 and 37, the grinding means 16 moves along an arcuate path in a counterclockwise direction towards the positioning means 19. The actuating means 33a is substantially similar to actuating means 33 and includes cylinder 36a, arm 37a, piston rod 38a, and pivot means 39a.

The grinding means 18 includes a grinding wheel 27b, a spindle motor housing 30b, atubular shaft 29b which is slidably received in a bearing housing 40 to allow axial movement of the grinding means 18 as the associated feed means 34b axially shifts the grinding means. Feed means 34b is attached to an arm 42 of an actuating means 43 for the grinding means 18. The arm 42 is pivotally mounted on a bearing block 44 which is mounted on the table 12. A'hydraulic cylinder 43a (FIG. pivots the arm 42 about the bearing block 44 to move the grinding wheel of the grinding means 18 relative to the positioning means 19. I

As each of the grinding wheels and respective grind? ing means l6, l7 and 18 is moved toward the positioning means 19, the wheels 27, 27a and 27b passes over its dressing means to remove a portion of a grinding surface 48, 48a, 48b and'to orient the grinding surface in the proper alignment to remove material from a workpiece 49 to give the desired orientation for a locating surface on the workpiece. As illustrated, the grinding wheel 27 forthe grinding means 16 cooperates with the dressing means which is a diamond block 20, the dressing means 21 cooperates with the wheel 27b of the grinding means 17and dressing means 22 cooperates with the grinding wheelI27b of the grinding means 18.

Referring to FIGS. 3 and 4, the workpieces 49, 49a and 49b are clamped in a workholder or shuttle box 50. As illustrated, the three workpieces are held in a spaced relationship with respect to one another and are illustrated as raw turbine blades produced either by casting or forging. The shuttle box 50 is illustrated as a split or two-part block having parts 50a and 50b which are clamped together to hold the workpieces 49, 49a and 49b. In forming the shuttle box 50, the parts 50a and 50b are provided with complementary surfaces 50c and 50d, respectively, for engaging the rough turbine blade portion of each of the workpieces 49 with the configuration of the complementary surfaces of the parts 50a and 50b holding each of the workpieces in the same orientation.

The workholder 50 is positioned on the positioning means 19and is clamped in a position relative to the dress blocks 20, 21 and 22 by cylinder 52. In the clamped position, the workholder 50 restsvon a lower support 53 and is held by the clamp 52 against an upright support 54. The upright support 54 and the lower support plate 53 are attached to a member 55 which is movable with respect to the upright frame 15. A bar 56 extends from the upper portion of the member 55 and has spaced stops 57 and 58. As illustrated, stop 57 is resting on an extension 59 of the upright frame 15 and limits the lowest position for the positioning means 19 comprising the movable member 55, the plates 54, 53 which support the workholder 50. The stop 58 when engaging an under-surface of the member 59 limits the maximum upward movement of the positioning means 19. The member 55 also supports a second upright member or bar 60 which has spaced trip means 61 and 62 which coact with limit switches 63 and-64 respectively as the positioning means 19 is moved to present theworkpiece 49a and the workpiece 49b respectively. Limit switches 63 and 64 which are supported on a member 65 are connected by electrical cables (FIG. 5) with a control box (FIG. 5) which is part of the control system of the device 10 and can be located in cabinet 23. To shift thepositioning means '19 from its first position to the second and third positions, respectively, an actuating means 66 is disposed on the frame 11 beneath the positioning means 19. As illustrated, a ram 67 of the actuating means 66 engages the lower plate 53 of the positioning means 19. Various types of actuating means can be utilized and a preferred actuating means 66, diagrammatically illustrated in'FIG. 5, comprises a pair of hydraulic cylinders 66a, 66b formed in a single housing with the first cylinder 66a having a piston connected'to the ram 67 and which piston has a stroke equal to the distance to position the second workpiece 49a in a grinding position at which time the trip 62 will actuate the limit switch 64. The second cylinder 66b contains a piston which is'connected to the frame and which acts to shift thehousing containing the first and second cylinder 66a and 66b and the piston rod such as ram 67 the next increment of distance upwardly necessary. to position the third workpiece 49b at which time the trip 61 actuatesthe limit switch 63. It should be noted that as the actuating means moves to actuate the limit switch 63, the stop 58 engages the member 59 to prevent any further upward movement.

In the preferred embodiment, it is desirable to move each of the grinding means l6, l7 and 18 at different rates of speed so that the respective grinding wheels 27, 27a and 27b are moved rapidly toward the workholder 50 until they reach a position with respect to their respective dressing means 20, 21 and 22 and then are moved in a slow feed while the surfaces 48, 48a, 48b

are dressed and subsequently engages the workpiece to remove the material to form the locating surfacesJThe preferred means for accomplishing this movement is by providing a plurality of limit switches which are engaged or actuated as each of the grinding means 16, 17 and 18 is pivoted through a specific amount or degree of its arc of travel. As illustrated in FIG. 5, thegrinding means 16 has three limit switches 74, and 76 which are electrically connected to the control means disposed in the box 70. The grinding means 17 has three limit switches 77, 78 and 79. and the grinding means 18 has three limit switches '80, 81 and 82. The

limit switches 74, 77 and 80 indicate when their respective grinding means 16, 17 and 18 are in the retracted or returned position which is illustrated in FIGS. 1 and 2. The limit switches 75, 78 and 81 are actuated when their respective grinding means 16, 17 and 18 have passed through the desired are at a rapid speed and are used to indicate when the speed of advance should be changed. The switches 76, 79 and 82 indicate when their respective grinding means 16, 17 and 18 have been advanced by its respective actuating means 33, 33a and 43 the desired distance and can be used by the control means to cause the return of the grinding means. As mentioned above, each of the limit switches is electrically connected in a control circuit utilizing a plurality of relays, time delays and the control system by using the signals received from the limit switches can control the sequence of the grinding steps.

To control the flow of fluid to each of the actuators, solenoid valves are actuated by electrical signals from the control means based on the inputs received from the various limit switches.

A diagrammatic example of the hydraulic means is best illustrated in FIG. 6. The diagrammatic illustration of the hydraulic control shows a hydraulic actuator 90 which comprises a piston 90a with a piston rod or ram and cylinder 90b. A fluid supply line 91 which is connected to the hydraulic pump such as 25 supplies hydraulic fluid under pressure and the fluid is ultimately returned by a drain or return line generally indicated at 92. The supply line 91 and the drain line 92 extends to a solenoid valve 93 which is biased by a spring to the position illustrated so that the hydraulic line 91 is connected to a line 94 and the drain line 92 is connected to a line 95. When the solenoid 93 is energized, the valve is shifted in the direction of the arrow 96 so that the supply line 91 is connected to the line 95 and the drain line 92 is connected to the line 94. As illustrated, the line 94 has a branch 97 which goes through a variable restricted orifice 98 and through a check valve 99 which are connected in parallel. Also extending parallel to the line 97 is a second line 100 which extends through a solenoid 101. The lines 97 and 100 are connected to a port 102 of the actuator 90. A second port 103 of the actuator is connected through a variable restriction 104 to the line 95.

In operation, when the solenoid valve 93 is actuated, the hydraulic line 91 is connected to the line 95 to supply fluid under pressure to the port 103 to cause the piston 90a of the actuator 90 to move in the direction of the arrow 105. In the position illustrated a trip 106 engages the limit switch 107. As fluid forces the piston 90a to move in the direction of the arrow 105, the trip 106 will engage an intermediate limit switch 108 which actuates electrical circuits to energize the solenoid valve 101. With the movement of the solenoid valve 101, flow through the passageway 100 to the drain line completion of the stroke of the actuator 90. At this time, the solenoids 101 and 93 are both deenergized allowing flow through the line and connecting the fluid input or supply line 91 to the line 94 and connecting the port 103 to the drain 92. The pressurized fluid flows through the line 91, the restricted orifice 98, the I check valve 99 and the passage or conduit 100 to the port 102 rapidly withdraw of force the piston 90a in the direction .of the arrow 110. The provision of the restricted orifice 104 provides a back pressure to limit the speed of the movement of the ram in the direction 110 and to provide a cushion to prevent slamming of the piston into the end of the cylinder 90b. It should be noted that as illustrated that the check valve 99 allows flow of fluid only when the line 97 is connected to the supply line 91. As mentioned above, besides causing the deenergizing of the solenoid 93 and 101, the limit switch 109 also is used to indicate when a next sequence or a next grinding element should be actuated.

As illustrated in FIGS. 1 and 2, the grinding means 16, 17 and 18 are arranged to provide three locating surfaces on each of the workpieces such as 49, 49a and 49b. The grinding means 16 and 17 provide or form the locating surfaces at and 116 as illustrated in FIGS. 3 and 4 and the grinding element 18 forms a locating surface 117 which is in a vertical plane. The locating surface 116 is in a horizontal plane and is substantially perpendicular to the vertical plane of the surface 117. The surface 115 lies in a plane which forms an angle A with the vertical plane of the surface 117, which angle is the same as the angle between the grinding surfaces 48 and 48b. As illustrated angle A is 90 and can be varied a predetermined amount on either side of 90. It has been found that a variation in the angle A between 85 and 95 provides a flexibility in providing locating surfaces on he workpiece with one surface being ground at an angle relative to the X and Y axes of the part.

To provide for the orientation of the surface 115 with respect to the vertical plane, the grinding means 16 is pivotally mounted on the frame 11 (FIG. 7) by an adjustment means generally indicated at 120 which enables the adjustment in the orientation of the axis of the grinding means 16 through an angle B of 10 to vary the angle A between the grinding surfaces 48 and 48b from 85 to 95. The adjustment means 120, which can be provided for any of the grinding means 16, 17 or 18, includes a base 121 rigidly attached to the table 12 of the frame 11 and a pivoting platform 122 formed by a pair of arms 123 which have a pivotal connection 124 to the base 121 at one end. A plate 125 extends between a pair of arms 123 and is connected thereto to provide a mounting base for the pivot means 39. To support the upper end of the pivot means 39, the adjustment means 120 includes an arm 127 attached to the plate 128 which has a slot 129 receiving a bolt 130 which attaches the plate 128 to an end plate 131 on the upstanding frame 15.

T o vary the orientation of the axis of the pivot means 39 and in turn to vary the angle A between the grinding surfaces 48 and 48b, the pair of arms 123 opposite the pivot connection 124 are provided with a bearing member 133 such as a dowel and the base 121 is provided with a machine surface 134 for receiving a block 135. To hold the bearing member 133 tightly against the block 135 and in turn the block 135 against the machine surface 134, a clamp means 136 such as a threaded member which extends through the bearing member 133, the block 135 and into the base 121 is provided. By changing the block 135 and replacing it with a block of a different thickness, the distance between the surface 134 and the bearing member 133 is changed to pivot the arms 123 about the pivot connection 124 and therefore vary the angle B and in turn angle A. Thus a set of blocks 135 with each block of a known thickness will provide a set of correspondingly known value for angle A and angle B.

To prevent play in the adjustment means 120 after a particular angle is achieved, the bolt 130 and bolts such as 140 are tightened. Since changes in the angle B causes the cylinder 36 and the piston rod 38 to be shifted relative to the upstanding structure, an adjustable connection means 141 may be provided if necessary for the pivot connection of the piston rod 38 to the upright structure 15.

When it is determined that a locating surface such as l should have a certain angle with respect to the vertical locating surface 117, the clamp 136 is removed, and the bolts 130 and 140 are loosened. The block 135 is removed and a block producing the desired angle is placed on the machine surface 134 and the clamp 136 replaced and engaged to hold the bearing member 133, the new block 135 and the machine surface 134 in tight engagement. Then the bolts such as 130 and 140 are tightened to remove any play in the adjustment means 120. Having completed these steps, the angle A between the grinding surfaces 48'and 48b is known and any subsequently formed locating surfaces 115 has the desired angular orientation between the surfaces 116 and 117.

The location of the material removing means 18 is such that it forms its locating surface 117 on the end of the workpiece 49 on which the grinding means 16 operates. If desired, a like grinding means 18 can be provided on the right hand side of the apparatus as illustrated in FIG. 1 to provide a locating surface similar to 117 on the end of the workpiece having a locating surface 116.

In some instances, it may be desirable to provide locating surfaces such as 115 and 117 on a workpiece along with an oriented drilled hole in the other end. In such situations, one of the grinding units such as 17 can be removed along with its dress block 21 and a center boring unit disposed on the table 12 with means for moving it into and out of engagement with a workpiece 49 held by the work holder 50.

In operation of the device, appropriate switches or start buttons on the switch box 24 are actuated to energize electrical systems to energize the spindle motors of each of the grinding means l6, l7 and 18, to actuate the hydraulic pump unit 25 of the hydraulic system, and to actuate a cooling system which sprays fluid such as cutting oils on the workpieces to prevent overheating during the grinding operation. After all these switches have been energized, a cycle switch is energized which causes the first step of the method for grinding workpieces 49.

During the first step, the grinding unit 16 is advanced toward the workpiece 49 at a rapid rate until limit switch is tripped at which time the control means actuates a solenoid similar to 101 in the hydraulic circuit illustrated in FIG. 6 to decrease the flow from an exhaust port of an actuator 33. With the limit switch 75 actuated the grinding means 16 is moved in a fine feed across the dressing block 20 to shape the grinding surface 48 and then into contact with the workpiece 49 to form or grind the locating surface 115. As the grinding means advances to its inward-most position of travel, limit switch such as 76 is tripped causing a reverse in the hydraulic flow to cause the withdrawal or return of the grinding means 16. With appropriate time delays in the control circuit, the tripping of limit switch 76 can also energize the signal to start or advance the grinding means 17 on its inward travel which will be at a rapid pace until limit switch 78 is tripped at which time a fine feed is used in moving the grinding means 17 toward the workpiece. The grinding wheel of the grinding means 17 is dressed by a dressing block 21 and then forms or grinds the locating surface 116. When the limit switch 78 is tripped, the feed of the grinding means 17 is reversed to return the grinding means to its return or retracted position illustrated in the drawings. When the grinding means 17 reaches its return position, the limit switch 77 is tripped which through the appropriate controls initiates the advance of the grinding means 18 which is rapidly moved toward the workpiece until the limit switch 81 is tripped at which time a slow feed of advance is initiated by appropriate changes in the hydraulic controls as described hereinabove. With a fine feed or slow advance the wheel 27b passes over the dress block 22 to dress the surface 48b, and to grind the surface 117 on the workpiece 49. When the limit switch 82 is tripped, the actuator for the grinding means 18 causes a reversal in the motion to return the grinding means to its rest position illustrated in the drawings.

At the time of hitting the return position which is indicated by tripping the limit switch thecontrol circuit will cause the actuating means 66 of the positioning means 19 to be actuated to raise the workholder to present a second workpiece such as 49a in position to be ground or machined. The tripping of the limit switch 80 by the return of the grinding means 18 can also be utilized to energize a circuit for advancing the axial feed means 34, 34a and 34b, of each of the grinding means 16, 17 and 18 the incremental distance necessary to provide a fresh surface on the grinding wheels 27, 27a and 27b for dressing during the next grinding pass. When the actuator means 66 by the ram of the cylinder 66a has positioned the shuttle box 50 so that the next workpiece 49a is in position for grinding, this is indicated by tripping of the limit switch 64 by the trip 62 and causes a repeat of the grinding cycle which include the grinding steps of the three grinding means 16, 17 and 18 and the advancing of the grinding wheel in the axial direction. Upon completion of the operation of the grinding means 18, during the repeat of the grinding cycle, the tripping of the limit switch 80 energizes the positioning means 66 to cause the cylinder 66b to raise the shuttle box 50 to present the workpiece 49b for grinding. It should be noted that appropriate electrical circuit means are utilized to cause the tripping of the limit switch 80 to actuate different items depending on the time of its tripping. Such circuit means can utilize an arrangement of time delays and/or energizing switches in the control means which arrangements are conventional.

After the positioning of the workholder 50 so that the workpiece 49b is in position for grinding, the grinding means 16, 17 and 18 are moved in the previously described sequence to provide the locating surfaces 115, 116 and 117 thereon. Upon completion of forming the locating surface 117, and with the retraction of the grinding means 18 to trip the limit switch 80 for the third time, the circuit arrangement is such to deenergize the actuator 66 to return the workholder to its original starting position and to then shut off the apparatus. An operator then unloads the shuttle box 50 and loads a new shuttle box containing unfinished workpieces. By restarting the device, grinding means will cycle through the sequence of steps to grind automatically the three newly loaded workpieces.

In the above description of the method, the grinding means 16 and 17 were actuated in a sequence with the grinding means 17 performing after the grinding means 16. The circuitry can be arranged so that the grinding means 17 and 18 perform their grinding operation prior v to the grinding means 16 with appropriate changes in the circuit arrangement for changing the control of repeating the cycle and positioning to be indicated by limit switch 74. Since both grinding wheels are grinding on opposite sides of a workpiece, both can be actuated simultaneously. The only requirement is that the grinding means 18 be in the retracted position during the actuation of the grinding means 16 due to the fact that the path of travel of the two wheels 27 and 27b cross each other. Another change can be initiated instead of advancing all of the grinding wheels axially by the feed means 34, 34a and 34b after the completion of the three grinding operations on the workpiece such as 49, each of the wheels can be fed or advanced axially upon return to the return position and the tripping of the respective limit switches 74, 77 and 80.

The apparatus and method of the present invention provides for the grinding of various locating surfaces by removing the material in a predetermined sequence of steps and repeating the grinding operations after repositioning a new workpiece into the grinding area. By utilizing the workholder or shuttle box 50 holding three workpieces, the apparatus will cycle three times to grind each of the workpieces in the desired sequence. Thus, the apparatus enables the operator to be free to load additional shuttle boxes or workholders 50 or to oversee the operation of a like machine while the present machine is performing its recurring grinding cycles.

Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to employ within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. A machining apparatus for forming a plurality of locating surfaces on a workpiece comprising: a frame, at least two grinding means, each of said grinding means having a grinding wheel mounted on a shaft for rotation on an axis of rotation with the grinding surface of each wheel being substantially perpendicular to the axis of rotation of the wheel, said grinding means having feed means for axially advancing the grinding surface, dress means for each of said grinding wheels for dressing the grinding surfaces thereof, said dress means being mounted on said frame, positioning means disposed on said frame for holding a workpiece in the desired orientation with respect to the dress means,

means for mounting each of the grinding means on the frame for movement along a path from a first position withdrawn from the workpiece and dress means to a second position with the axis of rotation of the grinding wheel remaining parallel and the path of one grinding wheel crossing the path of the other grinding wheel, said mounting means including an actuator means having a speed control means to move the grinding wheel from the first position to an intermediate position on the path at a first rate of feed and from said intermediate position across the dress means and into grinding engagement with the workpiece to the second position at a second rate of feed that is less then said first rate so that the grinding surface of the wheel is dressed by the dressing means prior to grinding the workpiece and grinds the workpiece at a slower rate of feed then when the wheel is moved from the first position to the intermediate position.

2. A machining apparatus according to claim 1 which includes a third means for removing material from a workpiece disposed on said frame with a third mounting means including means for moving the third material removing means relative to the workpiece held by the positioning means.

3. A machining apparatus according to claim 2 wherein said third material removing means is a grinding means.

4. A machining apparatus according to claim 1 wherein said mounting means for each of said grinding means comprises a pivotal mounting arm and wherein said actuator pivots said mounting arm to move the grinding wheel along its path.

5. A machining apparatus according to claim 1 wherein said speed control means includes limit switches to determine the position of said grinding means during its movement along said path.

6. A machining apparatus according to claim 5 wherein each of said actuator means is a hydraulic actuator having hydraulic lines connecting the actuator to a source of hydraulic fluid and to a drain, and wherein one of said lines has valve means actuated by one of said limits switch of the speed control means to change the rate of flow of the hydraulic lines to change the rate of feed of the actuator means.

7. A machining apparatus according to claim 1, which includes means for controlling the sequence of operation of said actuator so that one of said grinding means completed its grinding operation and is retracted to the first position before the actuator of the other grinding means moves its grinding wheel along the path from the first position.

8. A machining apparatus according to claim 7 wherein the positioning means includes a workholder for holding a plurality of workpieces in a predetermined spaced relationship and said positioning means further including means for holding said workholder in a plurality of predetermined position to sequentially hold each of said workpieces in the correct orientation 12 completion of the respective grinding operations prior to being utilized in a subsequent grinding operation.

10. A machining apparatus according to claim 1, wherein one of said means for mounting a grinding means includes adjustment means for changing the angular orientation of the grinding surface of said one grinding means relative to the orientation of the grinding surface of the other grinding means.

* l l l 

1. A machining apparatus for forming a plurality of locating surfaces on a workpiece comprising: a frame, at least two grinding means, each of said grinding means having a grinding wheel mounted on a shaft for rotation on an axis of rotation with the grinding surface of each wheel being substantially perpendicular to the axis of rotation of the wheel, said grinding means having feed means for axially advancing the grinding surface, dress means for each of said grinding wheels for dressing the grinding surfaces thereof, said dress means being mounted on said frame, positioning means disposed on said frame for holding a workpiece in the desired orientation with respect to the dress means, means for mounting each of the grinding means on the frame for movement along a path from a first position withdrawn from the workpiece and dress means to a second position with the axis of rotation of the grinding wheel remaining parallel and the path of one grinding wheel crossing the path of the other grinding wheel, said mounting means including an actuator means having a speed control means to move the grinding wheel from the first position to an intermediate position on the path at a first rate of feed and from said intermediate position across the dress means and into grinding engagement with the workpiece to the second position at a second rate of feed that is less then said first rate so that the grinding surface of the wheel is dressed by the dressing means prior to grinding the workpiece and grinds the workpiece at a slower rate of feed then when the wheel is moved from the first position to the intermediate position.
 2. A machining apparatus according to claim 1 which includes a third means for removing material from a workpiece disposed on said frame with a third mounting means including means for moving the third material removing means relative to the workpiece held by the positioning means.
 3. A machining apparatus according to claim 2 wherein said third material removing means is a grinding means.
 4. A machining apparatus according to claim 1 wherein said mounting means for each of said grinding means comprises a pivotal mounting arm and wherein said actuator pivots said mounting arm to move the grinding wheel along its path.
 5. A machining apparatus according to claim 1 wherein said speed control means includes limit switches to determine the position of said grinding means during its movement along said path.
 6. A machining apparatus according to claim 5 wherein each of said actuator means is a hydraulic actuator having hydraulic lines connecting the actuator to a source of hydraulic fluid and to a drain, and wherein one of said lines has valve means actuated by one of said limits switch of the speed control means to change the rate of flow of the hydraulic lines to change the rate of feed of the actuator means.
 7. A machining apparatus according to claim 1, which includes means for controlling the sequence of operation of said actuator so that one of said grinding means completed its grinding operation and is retracted to the first position before the actuator of the other grinding means moves its grinding wheel along the path from the first position.
 8. A machining apparatus according to claim 7 wherein the positioning means includes a workholder for holding a plurality of workpieces in a predetermined spaced relationship and said positioning means further including means for holding said workholder in a plurality of predetermined position to sequentially hold each of said workpieces in the correct orientation with respect to the dress means, and wherein said means for controlling including means to actuate said means for holding said workholder after all the grinding means have completed a grinding operation to shift said workholder between said predetermined position to position another workpiece for grinding.
 9. A machining apparatus according to claim 8 wherein said control means includes means controlling the feed means on the grinding means so that the feed means on each of the grinding means is actuated after completion of the respective grinding operations prior to being utilized in a subsequent grinding operation.
 10. A machining apparatus according to claim 1, wherein one of said means for mounting a grinding means includes adjustment means for changing the angular orientation of the grinding surface of said one grinding meanS relative to the orientation of the grinding surface of the other grinding means. 